1. Field of the Invention
The present invention relates to a test method for a print head of an ink jet printer.
2. Description of the Related Art
Japanese Laid-Open Patent Publication (hereinafter referred to as "OPI publication") Nos. SHO-48-9622 and SHO-54-51837 describe an ink jet recording device wherein a portion of ink in an ink chamber is rapidly vaporized to form an expanding bubble. The expansion of the bubble ejects an ink droplet from an orifice connected with the ink chamber. As described in the August 1988 edition of Hewlett Packard Journal and the Dec. 28, 1992 edition of Nikkei Mechanical (see page 58), the simplest method for rapidly heating the portion of the ink is by applying an energizing pulse of voltage to a heater. Heater described in the above-noted documents are constructed from a thin-film resistor and thin-film conductors covered with an anti-corrosion layer for protecting the resistor from corrosion damage. The anti-corrosion layer is additionally covered with one or two anti-cavitation layers for protecting the anti-corrosion layer against cavitation damage.
OPI publication No. HEI-6-71888 describes a protection-layerless heater formed from a Cr-Si-SiO or Ta-Si-SiO alloy thin-film resistor and nickel conductors. Absence of protection layers to the heater greatly improves efficiency of heat transmission from the heater to the ink. This allows great increases in print speed, i.e., in frequency at which ink droplets can be ejected. A print head wherein such heaters are used can be more simply produced.
Ink droplets can be ejected by applying only small amounts of energy to the heaters. The area surrounding the heaters will not be heated up by small amount of energy applied. Therefore, the LSI chip for driving the heaters can be formed near the heaters without fear of the LSI being damaged by overheating. OPI publication Nos. HEI-6-238901 and HEI-6-297714 describes an on-demand head with a simple monolithic structure wherein the LSI chip for driving the heaters is positioned near the heaters. The print head has many nozzles arranged two dimensionally at a high density. Also, the number of control wires is greatly reduced.
The present inventors realized that bubbles generated using the protection-layerless heaters have excellent generation and contraction characteristics. The present inventors also realized that these generation and contraction characteristics can greatly reduce cross-talk in a top-shooter or side-shooter thermal ink jet printer head driven using a new drive method. This indicates that the resistance to ink in the ink supply pathway can be reduced by shortening the length of individual ink channels for each nozzle. Since the ink supply pathway is shorter, the time to refill an ink chamber with ink after it is fired can be reduced so that printing speed can be increased.
The print head according to the present invention may appear to be analogous in structure to the print head described in OPI publication No. HEI-59-138472. However, where the OPI publication No. HEI-59-138472 describes a common channel for supplying ink to the ink ejection chambers as having a width in the range of 2 to 850 mm, the present invention has a common ink channel connected integrally to the individual ink channel formed in the same substrate, and the total width including the common ink channel and the individual ink channel is 0.2 mm.